The use of dialkyl fumarate-vinyl acetate copolymers as dewaxing aids

ABSTRACT

Copolymers of dialkyl fumarate and vinyl acetate having Specific Viscosities of at least 2.5 at 2% polymer concentration in xylene at 40° C., and wherein at least 50 wt. % of said alkyl groups are C 20  to C 24 , are useful as dewaxing aids, particularly in propane dewaxing.

BACKGROUND OF THE INVENTION

1. Field Of The Invention

The invention relates to copolymers of dialkyl fumarate and vinylacetate, wherein a major weight proportion of said alkyl groups are C₂₀to C₂₄ alkyl groups, which copolymers are useful in dewaxing oil,particularly in propane dewaxing processes.

2. Description Of The Prior Art

U.S. Pat. No. 3,729,296 discloses copolymers of long chain dialkylfumarate and vinyl acetate, as a wax crystal modifier, including use asa dewaxing aid.

U.S. Pat. No. 4,377,467 describes the use of different polymers asdewaxing aids including the use of mixtures of different dewaxing aidpolymers.

SUMMARY OF THE INVENTION The prese invention represents a furtherimprovement over U.S. Pat. No. 3,729,296 by the finding that forming thecopolymer within certain specific viscosity ranges improves theperformance of the polymer as a filtration aid in propane dewaxing.

The Copolymer

The dialkyl fumarate will have 50 to 100 wt. %, preferably 70 to 100 wt.% of its alkyl groups in the C₂₀ to C₂₄ range. The remaining alkylgroups may be either above C₂₄ or below C₂₀, such as groups derived fromtallow alcohols, or even methyl or ethyl alcohols, e.g., see U.S. Pat.No. 3,765,849. Behenyl alcohol is especially preferred for forming thefumarate. The copolymer is formed under nitrogen by a free radicalreaction by heating in a solvent the monomers together in aboutequi-molar proportions, with a free radical initiator, such as aperoxide. However, the overall conditions of time, temperature,peroxide, amounts of solvent, peroxide, etc. are chosen to form polymershaving a Specific Viscosity of about 2.5 to 8 or higher, e.g. about 2.7to 6, preferably 2.7 to 4.5, when measured as a 2 wt. % solution of thecopolymer in mixed xylenes at 40° C.

The Oil To Be Dewaxed

Any waxy petroleum oil stock or distillate fraction thereof may bedewaxed employing the dewaxing aid of this invention, although heavyfeedstocks are preferred. Illustrative but non-limiting examples of suchstocks are (a) distillate fractions that have a boiling range within thebroad range of from about 250° to 700° C., with preferred stocksincluding lubricating oil and specialty oil fractions boiling within therange of from between about 300° and 650° C. and (b) bright stocks anddeasphalted resids having an initial boiling point above about 425° C.Additionally, any of these feeds may be hydrocracked prior to distillingor deasphalting. These may come from any source such as paraffiniccrudes obtained from Aramco, Kuwait, the Panhandle, North Louisiana,etc., naphthenic crudes, such as Tia Juana, Coastal crudes, etc., aswell as the relatively heavy feedstocks such as bright stocks having aboiling range of 565+° C. and synthetic feedstocks derived fromAthabasca tar sands, Cold Lake crude, coal, etc.

The Dewaxing Process

A solution of dewaxing aid dissolved in an appropriate solvent such as alight heating oil or a light mineral oil fraction is mixed into thewax-containing oil and the mixture heated to a temperature higher thanthe cloud point of the oil (about 50° to 120° C.) This mixture isintroduced, along with the dewaxing solvent, into a chilling zone andchilled to a temperature necessary to yield the desired pour point forthe resulting dewaxed oil. The chilling produces a slurry comprisingdewaxed oil and solvent along with solid particles of wax which containthe dewaxing aid. This slurry is then sent to a wax filter to separatethe dewaxed oil and solvent from the wax particles.

The ratio of solvent to waxy oil would generally range from about 0.5 to10 and preferably from 0.5 to 3.0 volumes of solvent per volume of oil.The optimum amount of dewaxing solvent employed is of course determinedby the wax content of the oil, viscosity, pretreatment and dewaxingconditions.

The dewaxing aid is added to the waxy oil feed in an amount ranging fromabout 0.01 to 0.50 wt. % and preferably from about 0.02 to 0.2 wt. % ofthe oil.

Other dewaxing aids, each in similar amounts i.e. 0.01 to 0.50 wt. %,preferably 0.02 to 0.2 wt. %, based on the weight of oil may also beadded. Acryloid 150 which is a methacrylic acid ester polymer isfrequently used as such a co-dewaxing aid, e.g. see U.S. Pat. No.4,377,467, and has been found particularly useful with the fumaratevinylacetate copolymers of the invention.

The invention will be further understood by reference to the followingexamples.

EXAMPLES

A copolymer of behenyl fumarate and vinyl acetate having a SpecificViscosity of 3.0 when measured at a concentration of 2 wt. % polymer in98 wt. % xylene at 40° C. was prepared as follows:

Behenyl fumarate (456 g), vinyl acetate (148 g), and cyclohexane (372 g)are charged to a resin kettle and sparged with nitrogen. The mixture isheated under a nitrogen blanket to 75° C. with stirring until it iscompletely dissolved. Benzoyl peroxide (0.43 g) in ethyl acetate (˜ 10g) is sparged with nitrogen and added to the mixture. six hours thebehenyl fumarate is completely consumed and the reaction is quenchedwith 2,6-di-tert-butyl cresol (0.40 g). The yield of polymer based onbehenyl fumarate is 98%.

The above polymer, along with polymers of Specific Viscosity of 0.3,2.2, and 4.9 were tested in the propane dewaxing of a 600 Neutral Oil(600 SUS viscosity at 100° C.) under conditions simulating commercialplant operation. The oil was diluted with 1.4 to 1.6 volumes of propaneper volume of oil. The fumarate-vinyl acetate copolymer was added at atreat rate of 0.03 wt. % active ingredient (a.i.) of copolymer, based onthe weight of the oil. Acryloid 150 was also added as a co-dewaxing aidat a treat level of 0.040% a.i., based on the weight of oil. The testresults are summarized in the following Table 1.

                  TABLE 1                                                         ______________________________________                                        EFFECT OF BEHENYL FUMARATE-VINYL ACETATE                                      MOLECULAR WEIGHT ON DEWAXING PERFORMANCE                                      Specific     Feed Filter Dewaxed Oil                                          Viscosity    Rate (m.sup.3 /m.sup.2 /d)                                                                Yield (%)                                            ______________________________________                                        0.3           9          59                                                   2.2           9          64                                                   3.0          39          73                                                   4.9          32          71                                                   ______________________________________                                    

As seen by the above data, the higher Specific Viscosities gave a muchmore rapid filtration rate (and a higher yield of dewaxed oil. Filterrates of 39 cubic meters per square meter of filter surface per day (m³/m² /d) were obtained at 3.0 Specific Viscosity which appeared aboutoptimum with this oil.

What is claimed is:
 1. In a dewaxing process wherein a dewaxing aid ismixed with a waxy petroleum stock and solvent, and chilled to produce aslurry comprising dewaxed oil and solvent along with solid particles ofwax, and filtered to separate the dewaxed oil and solvent from the waxparticles, the improvement which comprises using as a dewaxing aid acopolymer of dialkyl fumarate and vinyl acetate having a SpecificViscosity measured at 2 wt. % solution in xylene at 40° C. of at least2.5, and wherein 50 to 100 wt. % of said alkyl groups are C₂₀ to C₂₄alkyl groups.
 2. In a process according to claim 1, wherein said solventis propane and wherein said dialkyl fumarate is behenyl fumarate.
 3. Ina process according to claim 2, wherein said Specific Viscosity is 2.7to 6.0.
 4. In a process according to claim 3, wherein said SpecificViscosity is about
 3. 5. In a process according to claim 1, wherein amethacrylic acid ester polymer is used as a co-dewaxing aid.